Many buildings require large access openings to permit the ingress and egress of large equipment, merchandise or flow of people into and from the structure. Covering these large openings requires large doors or windows (hereinafter collectively “doors”). Different types of doors have been developed to cover such openings, such as top or bottom slidably mounted doors supported by a roller/track system, vertically hinged doors, top hinged (overhead) doors, tilt-up doors (single panel doors hinged at mid-height for rotation about a horizontal axis) and bi-fold doors. Various means exist for actuating the doors between their open and closed positions, including man power, cables, screws or hydraulics.
In situations where there is limited available lateral or forward space from the door opening, use of each of these door types is problematic. For instance, large vertically hinged doors have a large arc of rotation and opening the door may be restricted by nearby obstacles. Similarly, slidably mounted doors require significant lateral extension of the horizontal support track(s) from the door opening to support the door when moved to an open position.
Top horizontally hinged doors are frequently utilized when lateral space to the door opening is limited or non-existent. However, these doors still require significant space in front of the door opening to be opened. Further, because of the distance these doors can extend outwardly when in an open position, these doors are susceptible to wind damage. Such doors frequently require significant structural support because they are heavy and leveraged out front of a building. A great deal of force is typically required to open and close these doors because of the door weight.
A version of a top horizontally hinged door that has reduced susceptibility to wind damage and reduced extension from the building is a bi-fold door. However, the main objection to use of a bi-fold door is the loss of headroom. When the door is in its open position, the bi-fold panels typically remain positioned in the upper part of the door opening, creating a height restriction in the door opening.
An objection to use of a single panel tilt door is the arc of swing at the bottom of the door, as it can intrude significantly into the space in front of the door opening. Additionally, the top edge of a single panel tilt-up door may rotate above the top of the door opening as the door is being opened, requiring a significant header area within the building.
Hydraulic cylinders provide ease of opening and closing single panel tilt-up doors. U.S. Pat. No. 8,539,716 to Betker discloses a single panel tilt-up door that utilizes a special top, lateral track that extends into a building. Rollers mounted on the top of the door are guided along the track when the door is opened. Hydraulic cylinders attached to the top end of the door are used to open and close the door.
There remains a need for an easy to open door system that requires no space lateral of the door opening and only limited space in front of the door opening and header space for the door to open, that absorbs many of the load forces created from opening and closing the door, is stable in windy conditions when the door is in an open position, and requires smaller, less expensive hydraulic cylinders to open and close the door.